Cumyl hydroperoxide, secondary oxidations

Complex (1) is a catalyst for selective oxidation of benzylic, allylic alcohols to aldehydes, and secondary alcohols to ketones using r-butyl hydroperoxide. Primary aliphatic alcohol oxidation failed. The use of cumyl hydroperoxide as radical probe discounted the involvement of i-BuO /t-BuOO. Hammett studies p = -0.47) and kinetic isotope effects kn/ku = 4.8) have been interpreted as suggesting an Ru—OO—Bu-i intermediate oxidant. 

Ruthenium tetroxide, generated in situ from a suspension of the dioxide in CCI4, by adding aqueous sodium metaperiodate, appears to be an excellent reagent for the oxidation of secondary alcohols in neutral or basic media. t-Amyl or cumyl hydroperoxide, with molybdenum pentachloride, readily oxidizes steroidal alcohols cholesterol affords the 5a-hydroxy-3,6-dione in good yield. ... 

Nitrones, C=N" (R)=0, are generated by the oxidation of N-hydroxyl secondary amines with 5% aq. NaOCl. ° Secondary amines, such as dibenzylamine, can be converted to the corresponding nitrone by heating with cumyl hydroperoxide in the presence of a titanium catalyst. Imines are oxidized to amides with mcpba and BF3 OEt2. ° ... 

Kinetic resolutions. A chiral alcohol is obtained on. selective removal of one enantiomer by acetylation using a chiral analog 1 of DMAP, or by oxidation based on hydrogen transfer to acetone mediated by a Ru complex 2. Benzylic secondary alcohols are resolved by selective pivaloylation with optically activeA-pivaloyl-4-t-butylthiazolidine-2-thione. A kinetic resolution of sulfoxides is based on asymmetric oxidation with (i-PrO)4Ti-cumyl hydroperoxide in the presence of a tartrate ester. Kinetic resolution of 1,3-diarylallenes is realized by selective oxidation with NaClO catalyzed by a chiral (salen)manganese(III) complex, whereas asymmetric hydrolysis of terminal epoxides with the aid of a chiral (salen)cobalt(II) catalyst solves the problem of their accessibility. 

Tertiary alkylhydroperoxides are used most often as oxidizing agents with alkenes since primary or secondary alkylhydroperoxides are susceptible to rearrangement and decomposition. Alkylhydroperoxides are relatively soluble in organic solvents, are more stable, and are easier to handle than hydrogen peroxide.256 Both TBHP and cumyl hydroperoxide are commercially available and widely used. As with hydrogen peroxide, reaction of alkenes with hydroperoxides usually requires transition metal catalysts in order to form... 

In this context, the NHPI-catalyzed oxidation approach has been widely investigated as an alternative route to the classical autoxidation process due to the evident opportunity to increase conversion and selectivity in the hydroperoxide, according to the catalytic cycle reported in Scheme 16.2. In particular, autoxidation of CU usually requires high temperatures in order to favor partial homolytic decomposition of the hydroperoxide for prolonging the propagation phase of the radical chain. The use of NHPI would allow operation under milder conditions, that is, temperatures lower than 100 C, limiting the formation of secondary products deriving from termination, such as cumyl alcohol and above all acetophenone. 

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